Properties Of Hybrid Knitted Composite T-beam Under Quasi-Static Bending And FEM Simulation

Knitted structures possess special structure and performance characteristics,such as mechanical properties and the whole formability.With a variety of new materials and finishing techniques,knitted composites have been widely used in industry,such as space aviation,ships,automobiles and construction.This paper reports hybrid knitted T-beam,expecting to combine the advantages of both weft-knit and warp-knit structure.Firstly, double faced interlock weft-knitted fabric was produced on the automated flat knitting machine using basalt fiber yarn.It shows that,with appropriate parameters of knitting,double faced interlock knitted fabric can be produced in nice appearances. Then the two knitted fabrics,double faced interlock weft-knitted fabric and biaxial warp-knitted fabric,were sewed together to form the hybrid knitted T-beam perform.After then,hybrid knitted composite T-beam was produced by VARTM(Vacuum Assisted Resin Transfer Molding) technique. The quasi-static bending tests on hybrid knitted composite T-beam was conducted at MTS810 with different rib heights.The experimental results obtained,including load - displacement curve and the failure of the composite T-beam.The results show that fabric structures and rib-height have significant effect on energy absorption of the composite T-beam. Based on the micro-structure of the hybrid knitted T-beam,a unit cell mode was built in this paper.Conducting the compliances matrix of the unit cell,and combining with the critical damage area(CDA) failure theory,a user defined material subroutine named VUMAT was developed to calculate the bending responses with a commercial finite element model(FEM) code ABAQUS.Load-displacement curves,deformations and failure mode calculated by the FEM were compared with those from experiments,and it shows a good agreement between experiment and FEM results.This method can be used to optimize the design for the hybrid knitted composite T-beam.